High di/dt, light-triggered thyristor with etched moat current limiting resistors

Abstract

The present invention is directed to a light-triggered thyristor having a high di/dt, high dv/dt, and high photosensitivity. The thyristor has a three-stage cathode emitter gating structure with integrated current limiting resistors. The current limiting resistors are defined by moats etched in the cathode base region. The moats also cause a "turn-on " current to flow through substantially all of the cathode base region.

We claim as our invention: 
     
       1. A light-triggered thyristor having a top surface, a bottom surface and an end portion extending therebetween, the thyristor being comprised of a first auxiliary cathode emitter region, a second auxiliary cathode emitter region, a main cathode emitter region, a cathode base region, an anode base region and an anode emitter region, a p-n junction between adjacent regions, an optical well disposed in a central portion of the top surface of the thyristor and extending into only said cathode base region, three moats disposed in the top surface of the thyristor disposed about and spaced apart from said optical well, said moats each extending only into said cathode base region, said moats defining, within said cathode base region two current limiting resistors. 
     
     
       2. The thyristor of claim 1 in which each of said current limiting resistors is comprised of two electrical resistors connected in a parallel circuit relationship. 
     
     
       3. The thyristor of claim 1 in which each of said current limiting resistors is comprised of two electrical resistors connected functionally in a parallel circuit relationship. 
     
     
       4. The thyristor of claim 3 in which one of said current limiting resistors is disposed electrically between the first auxiliary cathode emitter region and the second auxiliary cathode emitter region and the other current limiting resistor is disposed electrically between the second auxiliary cathode emitter region and the main cathode emitter region. 
     
     
       5. The thyristor of claim 4 in which the current limiting resistor disposed electrically between the first auxiliary cathode emitter region and the second auxiliary cathode emitter region is comprised of two electrical resistors connected in a parallel circuit relationship and the current limiting resistor disposed electrically between the second auxiliary cathode emitter region and the main cathode emitter region is comprised of two electrical resistors connected functionally in a parallel circuit relationship. 
     
     
       6. The thyristor of claim 4 in which the current limiting resistor disposed electrically between the first auxiliary cathode emitter region and the second auxiliary cathode emitter region is of a higher ohmic resistance value than the current limiting resistor disposed electrically between the second auxiliary cathode emitter region and the main cathode emitter region. 
     
     
       7. The thyristor of claim 1 in which, at full rated bias, the first auxiliary cathode emitter region will turn on the main cathode emitter region. 
     
     
       8. The thyristor of claim 1 in which the first auxiliary cathode emitter region is of such an effective area that current density is less than 1000 amps/cm 2  when the first auxiliary cathode emitter region is fully on.